One thing I don't really see a lot of in game nowadays is where the boss's healthbar and the protagonist's healthbar are displayed side by side. I was thinking about this because of Game Grump's recent play through of Castlevania and I noticed how boss fights in that game are very tense. There's this feeling of where you know you're going to die and the only way you'll survive is by killing the boss first and I think the way the healthbar is set up plays to this.

Now I've kind of forgot whether I'm talking about healthbars or about Castlevania's "me or them" style boss fights, so why don't we talk about both?

are you talking about how the health bar placement, or are you talking about boss fight?

If it's the health bar, placing your health bar alongside with the boss only work when your boss fight is like some kind of race to who die first. This works well with the old Castlevania up till Dracular X, because boss hit very hard and sometime to win a boss fight is to just kneel there and rapidly press the attack button, like for example when they fighting the Frankenstein Monster in Castlevania 1.

Forget about health bars for awhile, lets talk about the 2D Space that's available during Castlevania's boss fights; there's a reason why Castlevania's Reaper is the most vicious boss in video game history, the space that you can actually evade & attack is so limited that it raises the adrenaline in your heart.

Castlevania proves that 2D games can have better boss fights than 3D games just on the architectural space alone...its so limited & annoying yet so satisfying. To walk away with only inch of life left after most battles in Castlevania, Konami has done something right

Boss fights where it's impossible or close to impossible to avoid taking damage and basically turns into a damage race are pretty dumb, to be honest. Thankfully there aren't many real instances of this.

There is also the fact that the player character moves slowly, can't change his jump arc (depending on which game in the series), and must rely on a basic attack that uses precious frames of animation during which he's vulnerable. You are constantly weighing the advantage of getting one more crack of the whip in against the risk of getting hit during its animation by an enemy who can deal more damage than you can. It's what good gameplay is all about. Give the players tough choices. Make them weigh the pros and cons.

I find that it bugs me when I'm not sure how much health (or how many hits, or whatever) the boss has "left." Of course, it's also sort of distracting to have to keep glancing up at the corner of the screen throughout a fight. I can't tell you how many times in Bastion I died with all my health potions unused simply because I wasn't paying close enough attention to my own health, and trying to focus on the battles.I added health bars for both the player and (mini-)bosses in a game I'm currently working on, but I'm starting to feel like my testers aren't really paying attention to it anyways.What about other means of conveying health? Screens that dim red, for example. Any thoughts or preferences on that?

There are a lot of great things from a design standpoint that you get when displaying health bars. I recently picked up Dark Souls and it is one of the most frustrating and exhilarating single player experiences I have ever had. The boss battles are a large part of the experience.

The health bars tell you how much damage you are doing. This helps you weigh risk vs reward when performing powerful attacks, which often leave you vulnerable for a time.

The damage you inflict on the boss, and the damage the boss does on you places an "epic-ness" on the fight. How much stronger is this enemy than you? Imagine the rewards when you are victorious!

You can tailor your attacks based on damage you are doing. Is there a weak spot? Is there a way I can utilize the environment? How can I more efficiently destroy this beast?

The battle can have stages. Half, quarter, eighth health attack transitions. This offers a quick way to tell the player that the battle is going to change and they should be ready.

Finally your own health. Getting that clutch heal, block, or final blow is even better when you are inches or pixels from death.

I feel this style requires a deep and intuitive combat system. Few things kill the grandness of a boss fight like the lack of immersion you get from repeating the same action over, and over, and over as you watch the heath bar(s) tick down.

There are a lot of great things from a design standpoint that you get when displaying health bars. I recently picked up Dark Souls and it is one of the most frustrating and exhilarating single player experiences I have ever had. The boss battles are a large part of the experience.

The health bars tell you how much damage you are doing. This helps you weigh risk vs reward when performing powerful attacks, which often leave you vulnerable for a time.

The damage you inflict on the boss, and the damage the boss does on you places an "epic-ness" on the fight. How much stronger is this enemy than you? Imagine the rewards when you are victorious!

You can tailor your attacks based on damage you are doing. Is there a weak spot? Is there a way I can utilize the environment? How can I more efficiently destroy this beast?

The battle can have stages. Half, quarter, eighth health attack transitions. This offers a quick way to tell the player that the battle is going to change and they should be ready.

Finally your own health. Getting that clutch heal, block, or final blow is even better when you are inches or pixels from death.

I feel this style requires a deep and intuitive combat system. Few things kill the grandness of a boss fight like the lack of immersion you get from repeating the same action over, and over, and over as you watch the heath bar(s) tick down.

I can agree with you that having the health bar can help you figure out the risk and reward, but in the same way, look at how Monster Hunter done with their monster. You're basically a hunter trying to figure out how badly the monster hurts by just observing. I think it's more fun with that. Of course i don't say having health bar ruin stuff, but you should need it, most of the time.